A number of process variants have been proposed for processing waste incineration residues, wherein it has already been proposed inter alia to aftertreat waste incineration residues as incur in the form of slags or the like upon largely complete oxidation, by multi-stage reduction with nonferrous heavy metals being recoverable. With hitherto known processes each phase that has been depleted from metals could be granulated and added to a cement as a puzzolane.
Also the use of blast furnace slag in the course of cement production has already been prior art. Blast furnace slag stands out for its latent hydraulic properties and consequently may be added to a mixed cement immediately after appropriate comminuation or granulation. By appropriately treating blast furnace slag it is, however, also possible to directly aim at a defined cement quality, at least in terms of composition. Yet, in metallurgical operation also considerable amounts of steel slag incur, which are characterized by comparatively poor hydraulic properties. Therefore, such a steel slag, as a rule, calls for complex aftertreatment. The dumping of steel slag to an increasing extent gets problematic not least because of the chromium contents of such slags.